Ans. B. Superior canaliculusThe upper lacrimal system is close to the conjunctiva and fornix and is expected to be more affected by topical medications than the lower lacrimal system; this is now accepted as a fact in the literature. Topical agents including anti glaucoma medications such as timolol, pilocarpine and dorzolamide; antiviral drops such as idoxuridine and trifluridine; and systemic medications such as fluorouracil and docetaxel are now considered as risk factors for upper lacrimal system obstruction.puncti and canaliculi are the main anatomical sites of lacrimal drainage system obstruction associated with topical antiglaucoma medications, the common canaliculus and nasolacrimal duct may also be involved